1. Technical Field
This disclosure generally relates to active material actuators, and more particularly, to a quick-return active material actuator adapted for more rapidly returning a load, so as to decrease the de-actuation time of a system.
2. Background Art
Thermally activated active material actuators have been developed to more efficiently drive a load within a system, such as, for example, to drive the arm of a linkage system. In many applications, a reversible, or cyclic characteristic is often desirous and/or beneficial, wherein the load is caused to return to the original position as rapidly as possible. In these actuators, the oscillatory cycle produced is limited by the cooling period necessary to deactivate the actuator; wherein the cooling period is based, for example, on the cross-sectional area of the active material, and the heat transfer rate between the active material and its environment. Once the thermally activated actuator cools and deactivates, return elements such as antagonistically paired actuators, or biasing/energy storage elements (e.g., springs, etc.) are often used to return the load and reset the system. It is appreciated that where the actuator is caused to return prior to sufficiently cooling and deactivating, damage to the active material may result when threshold stresses are exceeded.
To reduce cooling period, and therefore, the de-actuation time of these systems, accelerated cooling measures have been developed, which include, for example, using forced air convection, and multiple actuators having smaller cross-sectional areas. However, these measures generally present various concerns in the art. For example, the addition of an ancillary cooling sub-system typically increases the complexity of the overall system, the packaging space required, and the operational/maintenance costs associated therewith. As such, there is a long felt need in the art for a thermally activated active material actuator that more efficiently reduces de-actuation time, thereby more rapidly effecting the return of a load.